Question: How to obtain all positions of member?

The member function can provide the position of x in table/list s for the first variable

 

e.g.

f:=[a,b,c,a,a];
member(a,f,'p');

will provide p=1

 

If I would like to know the position of all a, [1,4,5], is there any simple way to obtain them? I can do something like

 

n:=0;

for i from 1 to 5 do

 if f[i]='a' then

  n:=n+1;

  p[n]:=i;

 end if;

end do;

 

something like that

Thank you very much

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